This invention relates generally to microsurgical and ophthalmic systems and, particularly, to a control system which utilized various surgical instruments to a handpiece intended for ophthalmic surgical scissors of the "vertical" type, which handpiece can be activated by a foot pedal controlled linear solenoid motor and such handpiece's method of manufacture.
Present day ophthalmic microsurgical systems provide one or more surgical instruments connected to a control console. The instruments are often electrically or pneumatically operated and the control console provides electrical or fluid pressure control signals for operating the instruments. The control console usually includes several different types of human actuable controllers for generating the control signals supplied to the surgical instruments. Often, the surgeon uses a foot pedal controller to remotely control the surgical instruments.
The use of intraocular surgical scissors is well known. While manually operated scissors are still in widespread use worldwide, they suffer from the disadvantage of being subject to human limitations on speed and accuracy. The use of surgical scissors with electric motor drive is also widespread. Electrical motor driven scissors are divided into two well known types based upon the type of drive, those that are solenoid actuated and those that are driven by a direct current motor or "proportional" control.
Most intraocular scissors have design similarities in which a pair of cutting blades extend from the end of a tubular "needle", with one blade being fixed and the other, opposed blade end being reciprocated between an open and a closed position with respect to the fixed blade. This reciprocating motion is accomplished through the action of one of the driving systems mentioned, such as, for example, a manual or electric motor drive.
Electric motor drivers of either rotary or linear solenoid type activate scissor closure by controlled transfer of the motor energy to the movable blade. The scissors may be of the "vertical" design (the guillotine, or the parallel blade type), the angled or "horizontal" style, or of another design, or the driver may instead be used to actuate other instruments, besides scissors, that operate similarly.
The linear solenoid type of drive provides a reciprocating action in which the electrical actuation of a solenoid causes the movable blade to move to the closed position in relation to the fixed blade and then, usually through the operation of a spring within the hub of the scissors, to return to the open position. An example of a handpiece of this type is seen in the patent which issued to Lo et al., U.S. Pat. No. 5,275,607.
It is characteristic of solenoid actuated scissors handpieces that the cutting action provided be a rapid, snipping action, due to the fast firing of the solenoid plunger or piston. Thus, the solenoid actuated style of handpiece is appropriate for use with a surgical scissor of the known guillotine type, such as (as one example only) the scissor tip presently offered by STORZ.RTM. Ophthalmic Instruments Co. under the trademark ERGOTEC as product number E8700.
By contrast, when a more controlled instrument action is required, for example, for careful cutting or pinching, the proportional-type of motor and the incremental movement provided thereby is generally preferred. Thus, the proportional type of motor control, such as is provided by a stepper motor is appropriate for use when the operating instrument is a forceps or a conventional "horizontal" style of ophthalmic scissors or other instrument (e.g. ERGOTEC tip E8500 or E8600). Thus, the new handpiece described herein for use with a solenoid motor is capable of using a known type of surgical instrument tip, without the necessity of alteration or adaptation of the instrument.
An example of a known proportional control/handpiece is seen in U.S. Pat. No. 4,757,814, which issued to Wang et al., for a pneumatic cutting device. However, that device, although disclosed as proportional, includes a linear solenoid valve actuated by a selectively varied electrical signal generated by a power supply and controlled by a potentiometer which is in turn operated by a foot pedal.
One difficulty which occurs in manufacture of linear solenoid actuated handpieces for surgical instruments is related to the inconsistencies in product dimensions which necessarily occur during manufacture of parts. The differences of particular concern here are those that occur among solenoid piston lengths and between the lengths of actuating pins in surgical instruments of the type which are used in ophthalmic surgery. Variations between individual parts can cause even a new instrument to be non-functional, or to wear or operate improperly and break down prematurely, because the actuator pin is not met be the drive piston or because the actuator pin is driven too far.